/***********************************************************************************
Project: SHT1x/7x demo program (V2.4)
Filename: SHT1x_sample_code.c

Prozessor: 80C51 family
Compiler: SDCC (origin: Keil Version 6.23a)

Autor: MST
Copyrigth: (c) Sensirion AG
***********************************************************************************/
// Revisions:
// V2.4 calc_sht11() Coefficients for humidity and temperature conversion
//                   changed (for V4 sensors)
// calc_dewpoint() New formula for dew point calculation

#include <at89x52.h>
//#include <math.h> //Keil library
//#include <stdio.h> //Keil library
#include "main.h"

extern val_t cur_temp, cur_humi;

#define _nop_()                                 \
    __asm                                       \
    nop                                         \
    __endasm                                    \

typedef union {
    unsigned int i;
    float f;
} value;


//----------------------------------------------------------------------------------
// modul-var
//----------------------------------------------------------------------------------
enum {TEMP, HUMI};

#define DATA P3_5
#define SCK P3_4

#define noACK 0
#define ACK 1
//                         adr command r/w
#define STATUS_REG_W 0x06 //000 0011 0
#define STATUS_REG_R 0x07 //000 0011 1
#define MEASURE_TEMP 0x03 //000 0001 1
#define MEASURE_HUMI 0x05 //000 0010 1
#define RESET        0x1e //000 1111 0

//----------------------------------------------------------------------------------
static char s_write_byte(unsigned char value)
//----------------------------------------------------------------------------------
// writes a byte on the Sensibus and checks the acknowledge
{
    unsigned char i,error=0;
    for (i=0x80;i>0;i/=2) { //shift bit for masking
        if (i & value) DATA=1; //masking value with i , write to SENSI-BUS
        else DATA=0;
        _nop_(); //observe setup time
        SCK=1; //clk for SENSI-BUS
        _nop_();_nop_();_nop_(); //pulswith approx. 5 us
        SCK=0;
        _nop_(); //observe hold time
    }
    DATA=1; //release DATA-line
    _nop_(); //observe setup time
    SCK=1; //clk #9 for ack
    error=DATA; //check ack (DATA will be pulled down by SHT11)
    SCK=0;
    return error; //error=1 in case of no acknowledge
}

//----------------------------------------------------------------------------------
static char s_read_byte(unsigned char ack)
//----------------------------------------------------------------------------------
// reads a byte form the Sensibus and gives an acknowledge in case of "ack=1"
{
    unsigned char i,val=0;
    DATA=1; //release DATA-line
    for (i=0x80;i>0;i/=2) { //shift bit for masking
        SCK=1; //clk for SENSI-BUS
        if (DATA) val=(val | i); //read bit
        SCK=0;
    }
    DATA=!ack; //in case of "ack==1" pull down DATA-Line
    _nop_(); //observe setup time
    SCK=1; //clk #9 for ack
    _nop_();_nop_();_nop_(); //pulswith approx. 5 us
    SCK=0;
    _nop_(); //observe hold time
    DATA=1; //release DATA-line
    return val;
}



//----------------------------------------------------------------------------------
static void s_transstart(void)
//----------------------------------------------------------------------------------
// generates a transmission start
//       _____         ________
// DATA:      |_______|
//           ___     ___
// SCK : ___|   |___|   |______
{
    DATA=1; SCK=0; //Initial state
    _nop_();
    SCK=1;
    _nop_();
    DATA=0;
    _nop_();
    SCK=0;
    _nop_();_nop_();_nop_();
    SCK=1;
    _nop_();
    DATA=1;
    _nop_();
    SCK=0;
}

//----------------------------------------------------------------------------------
static void s_connectionreset(void)
//----------------------------------------------------------------------------------
// communication reset: DATA-line=1 and at least 9 SCK cycles followed by transstart
//       _____________________________________________________         ________
// DATA:                                                      |_______|
//          _    _    _    _    _    _    _    _    _        ___     ___
// SCK : __| |__| |__| |__| |__| |__| |__| |__| |__| |______|   |___|   |______
{
    unsigned char i;
    DATA=1; SCK=0; //Initial state
    for(i=0;i<9;i++) { //9 SCK cycles
        SCK=1;
        SCK=0;
    }
    s_transstart(); //transmission start
}

//----------------------------------------------------------------------------------
static char s_softreset(void)
//----------------------------------------------------------------------------------
// resets the sensor by a softreset
{
    unsigned char error=0;
    s_connectionreset(); //reset communication
    error+=s_write_byte(RESET); //send RESET-command to sensor
    return error; //error=1 in case of no response form the sensor
}

#if 0
//----------------------------------------------------------------------------------
static char s_read_statusreg(unsigned char *p_value, unsigned char *p_checksum)
//----------------------------------------------------------------------------------
// reads the status register with checksum (8-bit)
{
    unsigned char error=0;
    s_transstart(); //transmission start
    error=s_write_byte(STATUS_REG_R); //send command to sensor
    *p_value=s_read_byte(ACK); //read status register (8-bit)
    *p_checksum=s_read_byte(noACK); //read checksum (8-bit)
    return error; //error=1 in case of no response form the sensor
}

//----------------------------------------------------------------------------------
static char s_write_statusreg(unsigned char *p_value)
//----------------------------------------------------------------------------------
// writes the status register with checksum (8-bit)
{
    unsigned char error=0;
    s_transstart(); //transmission start
    error+=s_write_byte(STATUS_REG_W);//send command to sensor
    error+=s_write_byte(*p_value); //send value of status register
    return error; //error>=1 in case of no response form the sensor
}
#endif

//----------------------------------------------------------------------------------
static char s_measure(unsigned char *p_value, unsigned char *p_checksum, unsigned char mode)
//----------------------------------------------------------------------------------
// makes a measurement (humidity/temperature) with checksum
{
    unsigned char error=0;
    unsigned int i;

    s_transstart(); //transmission start
    switch (mode) { //send command to sensor
    case TEMP : error+=s_write_byte(MEASURE_TEMP); break;
    case HUMI : error+=s_write_byte(MEASURE_HUMI); break;
    default : break;
    }
    for (i=0;i<65535;i++) if(DATA==0) break; //wait until sensor has finished the measurement
    if(DATA) error+=1; // or timeout (~2 sec.) is reached
    //*(p_value) =s_read_byte(ACK); //read the first byte (MSB)
    //*(p_value+1)=s_read_byte(ACK); //read the second byte (LSB)
    // SDCC is little-endian !
    *(p_value+1) =s_read_byte(ACK); //read the first byte (MSB)
    *(p_value)=s_read_byte(ACK); //read the second byte (LSB)
    *p_checksum =s_read_byte(noACK); //read checksum
    return error;
}

//----------------------------------------------------------------------------------
static void calc_sth11(float *p_humidity ,float *p_temperature)
//----------------------------------------------------------------------------------
// calculates temperature [°C] and humidity [%RH]
// input : humi [Ticks] (12 bit)
// temp [Ticks] (14 bit)
// output: humi [%RH]
// temp [°C]
{
    const float C1=-2.0468; // for 12 Bit RH
    const float C2=+0.0367; // for 12 Bit RH
    const float C3=-0.0000015955; // for 12 Bit RH
    const float T1=+0.01; // for 12 Bit RH
    const float T2=+0.00008; // for 12 Bit RH

    float rh=*p_humidity; // rh: Humidity [Ticks] 12 Bit
    float t=*p_temperature; // t: Temperature [Ticks] 14 Bit
    float rh_lin; // rh_lin: Humidity linear
    float rh_true; // rh_true: Temperature compensated humidity
    float t_C; // t_C : Temperature [°C]

    t_C=t*0.01 - 40.1; //calc. temperature[°C]from 14 bit temp.ticks @5V
    rh_lin=C3*rh*rh + C2*rh + C1; //calc. humidity from ticks to [%RH]
    rh_true=(t_C-25)*(T1+T2*rh)+rh_lin; //calc. temperature compensated humidity [%RH]
    if(rh_true>100)rh_true=100; //cut if the value is outside of
    if(rh_true<0.1)rh_true=0.1; //the physical possible range

    *p_temperature=t_C; //return temperature [°C]
    *p_humidity=rh_true; //return humidity[%RH]
}

#if 0
//--------------------------------------------------------------------
static float calc_dewpoint(float h,float t)
//--------------------------------------------------------------------
// calculates dew point
// input: humidity [%RH], temperature [°C]
// output: dew point [°C]
{
    float k,dew_point ;

    k = (log10f(h)-2)/0.4343 + (17.62*t)/(243.12+t);
    dew_point = 243.12*k/(17.62-k);
    return dew_point;
}
#endif

//----------------------------------------------------------------------------------
void sht10_update(void)
//----------------------------------------------------------------------------------
// sample program that shows how to use SHT11 functions
// 1. connection reset
// 2. measure humidity [ticks](12 bit) and temperature [ticks](14 bit)
// 3. calculate humidity [%RH] and temperature [°C]
// 4. calculate dew point [°C]
// 5. print temperature, humidity, dew point

{
    value humi_val,temp_val;
    //float dew_point;
    unsigned char error,checksum;
    //unsigned int i;

    error=0;
    error+=s_measure((unsigned char*) &humi_val.i,&checksum,HUMI); //measure humidity
    error+=s_measure((unsigned char*) &temp_val.i,&checksum,TEMP); //measure temperature
    if(error!=0) s_connectionreset(); //in case of an error: connection reset
    else {
        humi_val.f=(float)humi_val.i; //converts integer to float
        temp_val.f=(float)temp_val.i; //converts integer to float
        calc_sth11(&humi_val.f,&temp_val.f); //calculate humidity, temperature

        cur_temp.si = temp_val.f * 100;
        cur_humi.si = humi_val.f * 100;
        //dew_point=calc_dewpoint(humi_val.f,temp_val.f); //calculate dew point
        //printf("temp:%5.1fC humi:%5.1f%% dew point:%5.1fC\n",temp_val.f,humi_val.f,dew_point);
    }
    //----------wait approx. 0.8s to avoid heating up SHTxx-----------------------------
    // for (i=0;i<40000;i++); //(be sure that the compiler doesn't eliminate this line!)
    //----------------------------------------------------------------------------------
}

void sht10_init(void)
{
    s_connectionreset();
}
